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| Technique of cracking control during immersion freezing of litchi fruit |
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| DOI：10.16768/j.issn.1004-874X.2016.08.021 |
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| Abstract: |
| Short shelf-life limits the development of litchi industry. Nowadays litchi fruits can be extended to more than 1 year with high quality preservation by using the new technology of immersion freezing（ IF）. But high fruit cracking rate was found in application of IF. In this study，based on analysis of the characteristics of cracked litchi fruit in the IF process，effects of the single factor of litchi variety，hot water blanching，vacuum degree or freezing temperature on fruit cracking rate were studied. Fruit cracking control in IF process was optimized by orthogonal experiment as well. Cracked suture was found to be the major type of cracking，constituted up to 67.67% of the cracking. Cracking rate of frozen Feizixiao（cv.） was only 10.29%，significantly lower than that of Huaizhi（cv.）and Guiwei（cv.），which was attributed to the unobvious suture，the thicker pericarp and the greater fracturing resistance of this cultivar. Treatment of hot water blanching for 5 s to 7 s，vacuum packing in - 0.085 MPa to - 0.092 MPa，or freezing at - 35℃ to -40℃ was found to preferably reduce the fruit cracking rate. The optimum technical combination would be hot water blanching for 7 s，vacuum packaging in - 0.085 MPa and IF at -35℃ based on the result of orthogonal experiment and freezing temperature was considered to to be the most significant factor on fruit cracking rate. The study contributed to improve IF technology and achieved a whole year preservation of litchi fruit，and therefore promoted litchi export of China. |
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